From the Midwest, USA and I'd would always refer to the date in the first way (and subsequently, it is logical to write the date in month/day format).
Still agree that day/month/year makes more sense.
Example with lots of written dates: http://www.telegraph.co.uk/news/2017/03/29/article-50-brexit... (but I could equally choose a formal document, like my birth certificate, or something very informal, like a handwritten note).
When spoken, the "of" is always included, and the number is always an ordinal (-th etc).
And year/month/day/hour/minute/second is best as its largest to smallest and if you name your documents / fields in this format it sorts better.
The latter. "April fourth" would sound very odd in a British accent.